Does anyone know how these two concepts are related? Where was the origination of Ueshiba's usage of the square, circle, and triangle?

I'm not sure, but I know they're major concepts in Shinto, representing a wide variety of relationships: http://tsubakishrine.org/aikido/index.html
The part I suspect is most applicable to waza is the -no-irimi mentioned in the index. How to articulate the differences I'm not so sure, but this video might help a little:http://www.youtube.com/watch?v=xc3nrMBLWsY
I'm not sure which form of entry Barrish sensei is talking about, but at one point he says it's not the chokusen no irimi (square).